Hydraulic supports



Nov. 15, 1960 11555 ETAL 2,959,922

HYDRAULIC SUPPORTS Filed July 28, 1958 2 Shgets-Sheet 1 lnvenlor! 6:1088 cumgw l /211;" My

Nov. 15, 1960 B. TEBB ET AL 2,959,922

HYDRAULIC SUPPORTS Filed July 28, 1958 2 Sheets-Sheet 2 Z a/1 9 1 can/cs1mm) United States Patent HYDRAULIC SUPPORTS Bernard Tebb, StaddlestonesGarth, Swanland, and Clarence Herbert Perry, Hull, England, assignors toMastabar Mining Equipment Company Limited, Hull, Yorkshire, England, aBritish company Filed July 28, 1958, Ser. No. 751,475 Claims priority,application Great Britain July 30, 1957 2 Claims. (Cl. 60-52) Thisinvention concerns hydraulic supports, that is to say supports in whicha pair of relatively movable members are telescopically extendible andcollapsible due to the flow of hydraulic fluid between a reservoir and ahydraulic pressure chamber associated with said members; and relatesparticularly to supports of this type which constitute roof supports orpit props for use in mining operation, and wherein the fluid flow forcollapse of the support is via ports, tubes, channels or the likepassing through a ram or piston between the relatively movable members.

It is not an uncommon experience with such hydraulic supports that therate of collapse is not adequate for rapid withdrawal of a support fromone position and quick resetting thereof for use in another position,primarily due to the small cross-sectional areas of the ports, tubes,channels or the like as compared with the crosssectional areas of therelatively movable members, resulting in restriction of the fluid flowfrom one side of the piston or ram to the other.

According to the present invention, therefore, the ram or piston betweenthe two relatively movable members comprises two mutually separableparts, and manually operable means accessible externally of the supportare provided to enable said parts to be mutually displaced to createtherebetween a fluid flow passage providing for substantiallyunrestricted fluid flow from one side of the ram or piston to the otherside thereof.

The invention may conveniently be employed with that type of telescopichydraulic support wherein one of the relatively movable members servesas a hydraulic pressure chamber and the other member, which carries oracts as the ram or piston, serves as a hydraulic reser voir and isslidable within the pressure chamber in dependence upon the flow offluid therein.

The invention will be decribed further, by way of example, withreference to the accompanying drawings, in which:

Fig. 1 is a vertical longitudinal section through a pit prop embodyingthe invention, and showing a twopart ram in closed condition; and

Fig. 2 is a similar section with certain parts broken away and showingthe ram in open condition.

In the embodiment of the invention shown in the drawings, a pit propincludes a first hollow elongated cylindrical member which at one endpresents the base 12 of the prop, and which at its opposite endslidingly receives a second, similar member 14, the upper end of whichpresents the supporting head as at 14a of the prop. The cylindricalmember 10 is employed as a hydraulic pressure chamber, and the secondcylindrical member 14 as a fluid reservoir; and hydraulic fluid ispumped from the reservoir space 16 of the member 14 into the workingspace 18 of member 10 by means of a hydraulic pump generally designated20 and located at the inner end of the member 14. This inner end ofmember 14 is constructed to constitute a hydraulic ram against whichacts the fluid pressure generated in the working space 18.

The ram carries a peripheral oil sealing ring 22 hydraulically isolatingthe reservoir space from the working space, and the pump 20, which isoperable by manual means accessible externally of the prop, mayconveniently be mounted on the ram itself.

In accordance with the proposal made by the invention, this ram isconstructed substantially in two main parts, an outer part 24 carryingthe aforementioned sealing ring 22 and slidable within the firstcylindrical member 10, and an inner part 26 carrying the pump 20 anddisplaceable from the outer part 24 in order to create (Fig. 2) a fluidflow passage 28 when hydraulic fluid under pressure in the working space18 is to be rapidly allowed to return to the reservoir space 16 for thepurpose of collapsing the prop from an extended condition. The outer rampart 24 is hollow and is provided towards one and region of its internalcylindrical wall with an annular recess 30, and the inner ram part 26,which is solid, has an annular flange 32 adapted to operate in butofless axial depth than the said recess 30. This annular flange 32carries an upper hydraulic fluid sealing ring 34, and the annular recess30 in the outer ram part houses spring means 36 arranged resiliently tourge the said annular flange together with the sealing ring, 34, intoabutment against the upper wall of the recess.

At the top of the inner part 26 of the ram is carried a pump cylinder 38wherein is slidingly arranged a pump piston 40 carrying a clevis 42 towhich is pivotally secured a connecting rod 44 arranged axially withinthe reservoir space 16 and adapted for operative connection, at its endremote from the pump piston 40, with a handle (not shown) positionedexternally of the support, the handle being arranged for reciprocationbetween a pair of limiting positions, which typically may be some 45above the horizontal to 45 below the horizontal. By way of example, theconnecting rod 44 is shown diagrammatically as being engaged at itsupper end with a crank pin 46 of a crank 48 pivotally mounted in thecylindrical wall of the member 14, the crank being formed externally ofthe member 14 with a square recess 50 adapted to receive a co-operatingkey presented by the said handle. At its lower position, shown in dottedlines in Fig. 1, the pump piston 40 abuts against the bottom of the pumpcylinder 38 which is, of course, constituted by the top of the innerpart 26 of the two-part hydraulic ram, and

considerable resistance to further depression of the handle isexperienced due to the springs 36 which urge the two ram parts 24 and 26together, this resistance being all the greater if the prop issupporting a load and hence there is pressure in the working space 18.If, however, there is no load on the prop, further depression of thehandle beyond its normal 45 lower limit causes the piston 38 to depressthe inner ram part 26 so as to separate the same from the outer part 24and create the fluid flow passage 28, thereby enabling hydraulic fluidto pass with a minimum of resistance from the working space 18 to thereservoir space 16, and in consequence, due to the weight of the secondcylindrical member 14 and its ram, permitting a rapid drop of the latterwithin the first cylindrical member 10. Thus a prop from which a loadhas been removed, but which is still in an extended condition, mayrapidly be collapsed and made ready for resetting in a new position.

If convenient in any particular construction of hydraulic supportembodying the invention, the inner part of the ram 26 may includesuction and delivery ports 52 and 54 with valves 56 and 58 for the pump,and an excess pressure relief valve (not shown) allowing the support toyield under a predetermined maximum load.

We claim:

1. In a hydraulic support of the type having a hollow outer memberdefining a pressure chamber, an elongate Patented Nov. 15, 1,960

hollow inner member telescopically received within one end of said outermember and having an inner end projecting into said pressure chamber,and means for controlling the flow of pressure fluid between theinterior of said hollow inner member and said pressure chamber; theimprovement wherein said means for controlling flow comprises a housingdefining a piston chamber opening at one end into the interior of saidinner member and having a first valve controlled flow passage forconducting fluid from the other end of said piston chamber through saidhousing into said pressure chamber, said housing having a second valvecontrolled flow passage therein for conducting fluid from the interiorof said inner member to said other end of said piston chamber, meanssupporting said housing within an opening in said inner end of saidinner member for relative sliding movement longitudinally of said innermember, shoulder means on said housing engageable with said inner memberto limit sliding movement of said housing into said inner member andoperable when engaged with said inner member to seal said opening fromsaid pressure chamber, means normally maintaining said shoulder means inengagement with said inner member, a piston mounted within said pistonchamber for reciprocating movement longitudinally of said inner memberto pump pressure fluid from the interior of said inner member into saidpressure chamber via said flow passages, means for reciprocating saidpiston in a normal working stroke between the ends of said pistonchamber, said reciprocating means being movable to an abnormal positionto engage said piston with said other end of said piston chamber todrive said housing outwardly of said inner member to thereby disengagesaid shoulder means from said inner member and place said pressurechamber in direct fluid communication with the opening in said innermember.

2. A hydraulic support as defined in claim 1 wherein said means normallymaintaining said shoulder means in engagement with said inner end ofsaid inner member comprises an extension on the inner end of said innermember, and spring means seated in compression between said extensionand said shoulder means to resiliently maintain said shoulder meansseated against said inner member.

References Cited in the file of this patent UNITED STATES PATENTS

